Ribbon hub and spool assembly

ABSTRACT

A ribbon hub and spool assembly includes a hub having at least two cantilever beams having a smooth, tapered, and curved crown, and a spool having curved and tapered splines. The cantilever beams balance the forces when inserting the hub into the spool, and the shape of the crowns of the hub and splines of the spool enable easy insertion and alignment of the hub and spool assembly.

CROSS REFERENCE TO RELATED APPLICATIONS

The present invention claims priority to U.S. Provisional Application Ser. No. 60/692,197, filed Jun. 17, 2005, and which is incorporated by reference in its entirety.

BACKGROUND

1. Field of Invention

The present invention relates to a printer ink ribbon spool and hub assembly.

2. Related Art

Impact printers incorporate inked ribbon to supply ink for the printing process. Typically this inked ribbon is provided as a long length of fabric wound-up onto a supply spool, or it is stored inside a cartridge in one long continuous loop. During the printing process, the inked ribbon, whether on spools or in a cartridge, is pulled through the printing station by means of one or more motor-driven hubs that engage splines in the spools or cartridge.

The ribbon system, including the inked fabric and its associated cartridge or set of spools, is a consumable product that must be periodically replaced. Replacement of the ribbon involves lifting the cartridge or spools from motor driven hubs, and re-installing a new cartridge or spools onto those hubs.

FIGS. 1 to 5 show a conventional spool and hub assembly 10. Assembly 10 includes a spool 12 (FIGS. 3 and 4) and a hub 14 (FIGS. 1 and 2). As shown in FIG. 1, hub 14, which is typically motor-driven, has one or more axially oriented splines 16. Splines 16 engage similar splines 18 within spool 12 (as shown in FIG. 3) or drive rollers within the cartridge, i.e., splines 16 of hub 14 fit in the groove between splines 18 of spool 12. Hub 14 also has a snap feature that prevents the spools or cartridge from moving axially on the hubs. In this way the vertical alignment of the ribbon with respect to the printing station is assured. In the reciprocating spool design, this alignment is crucial.

There are a few aspects of the ribbon removal and replacement procedure that are problematic for the user, to which this invention is addressed. In the present art, most or all ribbon drive hubs contain a single, cantilever beam type 20 of locking feature. This beam must be deflected towards the central axis of the hub (or pushed inward) in order to remove or install a ribbon. The deflection force is typically applied by pushing against beam 20 with the spool as it is being installed, or by deflecting beam 20 with the thumb while lifting the spool away from the hub. Because it is a single beam, the force required to deflect the beam is not counter-balanced with an opposing force, making the procedure awkward and difficult. FIG. 5 shows spool 12 and hub 14 assembled and locked. As seen, to remove hub 14 from spool 12, the user has to depress beam 20, while also pushing hub 14 and spool 12 away from each other.

Installment of a new spool or cartridge is also complicated by the need to visually or tactilely align spool splines 18 between hub splines 16. This alignment involves rotating the spool or drive roller so that the splines properly interleave. In a cartridge application, because the internal splines within the cartridge cannot be accessed or seen, this alignment can be very difficult if the deflection of a cantilever snap feature is involved.

Therefore, there is a need for a printer ribbon spool and hub assembly that overcomes the disadvantages discussed above.

SUMMARY

According to one aspect of the present invention, a hub and spool assembly includes a hub having two or more tapered cantilever beam snaps, a tapered top portion, and rounded splines along the circumference of the hub, and a spool having a plurality of rounded and tapered splines along a tapered interior of the spool. Such a hub and spool assembly provides numerous advantages over conventional assemblies.

The plurality of cantilever beam snaps enables opposing forces to balance the loads when the beams are deflected during spool or cassette installation. A tapered, rounded, or smoothly blended crown or ridge on the top of the cantilever beam snaps lets the user more easily begin insertion of the hub into the hole of the spool. This also, in conjunction with the rounded splines of the hub and the rounded, tapered splines of the spool allows for self-alignment, resulting in an easier alignment of spool and hub. The tapered edge along the opening of the spool enables easy insertion of the hub. In addition, once “locked”, the geometry of the beam snaps and tapered edge allows the hub to be removed by simply pushing out the hub, thereby eliminating the need to directly depress the beam snaps.

In another embodiment, the crown of the beam snaps have a tapered lower portion so that the spool does not need to have a tapered edge along the opening. The tapered lower portion would rest against the spool when the hub and spool are “locked”. The tapered lower portion would then similarly allow the user to remove the hub by simply pushing out the hub, since the physical action of pushing out the hub causes the cantilever to depress for easy removal.

Embodiments of the present invention and their advantages are best understood by referring to the detailed description that follows.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view of a conventional motor-driven hub;

FIG. 2 is a top view of the hub of FIG. 1;

FIG. 3 is an enlarged view of the hole of a conventional ribbon spool showing splines located therein;

FIG. 4 shows the hub of FIG. 1 being inserted into the spool of FIG. 3;

FIG. 5 shows the hub of FIG. 1 fully inserted into the spool of FIG. 3;

FIG. 6 is a side view of a motor-driven hub according to one embodiment of the present invention;

FIG. 7 is a perspective view of the hub of FIG. 6;

FIG. 8 is a top view of the hub of FIG. 6;

FIG. 9 is an enlarged view of the splines along the interior of a spool according to one embodiment of the present invention; and

FIG. 10 shows the hub of FIG. 6 being inserted into the spool of FIG. 9.

It should be appreciated that like reference numerals are used to identify like elements illustrated in one or more of the figures.

DETAILED DESCRIPTION

According to one embodiment of the present invention, a hub and spool assembly for a printer system includes a hub with at least two tapered cantilever beams, rounded splines, and a tapered top, and a spool having rounded and tapered splines and a tapered opening.

FIG. 6 is a side view of a hub 100 according to one embodiment of the invention. FIG. 7 is a perspective view of hub 100, and FIG. 8 is a top view of hub 100. Hub 100 can be a motor-driven hub for use in an impact printer system. In this embodiment, hub 100 has a top flat surface 102 with an angled or tapered portion 104 extending to the outer circumference of the hub. A plurality of splines 106 is located along the outer circumference of the hub, where splines 106 extend parallel to the axis of rotation. Each spline 106 has a rounded or curved top portion 108 at or near angled portion 104.

Hub 100 also has two opposing cantilever beams 110. Other embodiments can have more than two such beams. Beams 110 are attached to the base or a bottom portion of hub 100. The bottom portion of hub 100 has a ledge 111 with a larger circumference than the body of the hub. Hub 100 has recessed portions corresponding to beams 110 so that an upper portion of beams 110 can be flexibly pushed into the center of hub 100. In other words, when no force is applied to beams 110, there is a gap in the recessed portion between the center of the hub and the beams. Both hub 100 and beams 110 can be made by molding plastic or other suitable material. The opposing beams enable forces to be balanced when inserting the hub into a corresponding spool, where insertion pushes the beams toward the center of the hub.

Cantilever beams 110 have a top portion or crown 112 extending above top surface 102 of hub 100. Crown 112 has a tapered point 114 and a curved outer surface. Tapered point 114 extends down a center ridge to flattened portion 116 having a width a little less than the width between splines of the spool, as will be discussed below. Tapered point 114 enables easy alignment with the spool. The curved outer surface, center ridge, and angled portion 104 enable easy and smooth insertion into the spool. Flattened portion 116 enables secure alignment with the spool. In one embodiment, one of the cantilever beams has a guide portion 118 having a width approximately the same as the width of flattened portion 116, i.e., a little less than the width between splines of the spool, extending along a central portion of the beam. Guide portion 118 extends to approximately the same plane as flattened portion 116. This additional guide portion 118 engages with the groove between splines of the spool for easy insertion and stable alignment.

FIG. 9 shows an interior portion of a spool 200 according to one embodiment of the present invention. Spool 200 has a hole which hub 100 fits through. A plurality of splines 202 is located along the interior portion or hole of spool 200. In one embodiment, spool 200 has a small beveled or tapered ring 204, where the taper extends from the surface of the spool into the hole. Tapered ring 204 is present on both sides of spool 200. Splines 202 have curved tapered ends 206 at both ends extending to the edge of tapered ring 204. In other words, the ends of the splines are sloped downward toward the tapered ring. The combination of the tapered ring and curved tapered ends of the splines enables easy insertion and alignment of the hub.

FIG. 10 is a top view showing hub 100 being inserted into spool 200. In operation, hub 100 is first pushed into the opening of spool 200. Initially, the tapered point of the crowns contacts the interior surface of the spool. The tapered ring of the spool and the curved and tapered crown allows the user to easily insert the hub into the spool. The two opposing cantilever beams are then forced together as the hub is continually inserted into the spool. The force from the cantilever beams are balanced so that the user simply needs to push the hub into the spool to engage the beams against the spool. This is in contrast to hubs having only one cantilever beam, which can make both initial and continued insertion difficult.

As the hub is continually pushed into the spool, the hub quickly self-aligns with the splines of the spool. The curved and tapered crowns and center ridge position themselves into the grooves between splines of the spool. Continued insertion slides the splines of the hub and the flattened portion and guide portion of the cantilever beams along the grooves between the splines of the spool. When the bottom ledge of the hub contacts the spool, the hub is completed inserted into the spool. The crown of the cantilever beams are then released from the inner portion of the spool and expand over the surface of the spool.

When removing the hub from the spool, the user simply pushes the hub back out. The opposing cantilever beams balance the force for an easier movement. The tapered ring on the spool engages and pushes inward the crown of the cantilever beams, thereby eliminating the need for the user to directly push together the crowns for hub removal. In other embodiments, the bottom of the crowns may be tapered upward, with the spool having no tapered ring. This would also enable the user to push out the hub without directly pushing in the crowns.

Having thus described embodiments of the present invention, persons skilled in the art will recognize that changes may be made in form and detail without departing from the scope of the invention. For example, the figures show numerous features for both the hub and spool. However, not all are required to achieve advantages over conventional hub and spool assemblies. Further, the figures show two cantilever beams directly opposing each other. Embodiments with more than two beams are also suitable, with each beam spaced equally in angle from each other so that forces are balanced. For example, if three beams are used, each beam would be 120° apart. Thus the invention is limited only by the following claims. 

1. A ribbon hub and spool assembly, comprising: a hub, comprising: a cylindrical body having at least two recessed portions; at least two flexible beams, each beam having a first end attached to a bottom portion of the cylindrical body and a second end attached to a curved and tapered crown, wherein the beams are radially movable within the recessed portions; and a top portion; and a ribbon spool, comprising: opposing flat discs; a cylindrical ring connecting the two flat discs, wherein the cylindrical ring has an inner surface and an outer surface; and a plurality of splines along the inner surface of the ring, wherein the splines have at least one curved and tapered end.
 2. The assembly of claim 1, wherein the hub further comprises a plurality of splines having curved ends extending toward the top portion.
 3. The assembly of claim 1, wherein the crown has a narrow tip tapering laterally and radially outward, a guide portion having a width corresponding to a portion between the splines of the spool, and a center ridge extending from the narrow tip to the guide portion.
 4. The assembly of claim 1, wherein at least one of the beams has a guide portion below the crown and extending outward, wherein the guide portion has a width corresponding to a portion between the splines of the spool.
 5. The assembly of claim 1, wherein the hub further comprises a bottom portion have a ledge with a larger circumference than the cylindrical body.
 6. The assembly of claim 1, wherein the spool further comprises an angled annular surface connecting the cylindrical ring with the flat disc.
 7. The assembly of claim 1, wherein the flexible beams oppose each other.
 8. The assembly of claim 1, wherein the top portion has a circumference smaller than the cylindrical body and an angled surface tapering toward the outer circumference of the cylindrical body.
 9. A hub and spool assembly for a ribbon printing system, comprising: a hub having at least one spline with a curved end, at least two movable beams parallel to the spline, and a smoothly curved and tapered crown at the end of each beam; and a spool having a plurality of curved and tapered splines along an interior portion of the spool, wherein the spline and crowns of the hub fit between the splines of the spool during an assembly of the hub and spool and when the hub and spool are fully assembled.
 10. The assembly of claim 9, wherein the spool further comprises an angled annular surface between the curved and tapered portion of the splines and one of two planar surfaces of the spool.
 11. The assembly of claim 9, wherein the hub further comprises an annular surface angled inward from the curved end of the spline to a top surface of the hub.
 12. The assembly of claim 9, wherein at least one of the beams comprises a guide portion extending outward from the beam.
 13. The assembly of claim 9, wherein at least one of the crowns comprises a guide portion extending from a bottom portion of the crown.
 14. The assembly of claim 9, wherein the hub further comprises a bottom ledge extending beyond the at least one spline.
 15. The assembly of claim 9, wherein the beams are connected to a bottom portion of the hub.
 16. The assembly of claim 9, wherein the crowns extend above a top surface of the hub. 